Pool swim season in Clearlake, CA
When can you swim in an outdoor pool in Clearlake, CA?
An unheated pool in Clearlake never reaches 78°F in a normal year. It peaks around 77°F in Aug. The air allows up to 6 swimmable months with a heater (May to Oct).
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Heater options for a Clearlake pool, side by side
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 0 | no month | $0 | $0 |
| Solar cover only | 3 | Jul to Sep | $0 | $50 |
| Solar panels + cover | 4 | Jun to Sep | $0 | $283 |
| Heat pump + cover | 6 | May to Oct | $598 | $1,148 |
| Gas heater + cover | 6 | May to Oct | $764 | $1,189 |
For a 450 sq ft pool held at 80°F, at CA prices of 32.6¢/kWh electricity and $22/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Clearlake
Heat pump + cover: 6 of 6 possible months for about $1,148 a year all-in, which works out near $191 for each month it adds.
Before you pay for any heater, buy a solar cover: on its own it adds 3 months here for about $50 a year (why a cover comes first). If you get quotes, ask for a heat pump sized to your pool's surface area; here it beats gas all-in (heat pump or gas).
Weather station: Clearlake 4 SE, 4.3 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Clearlake month by month: air, sun and pool water
| Month | Air high | Air avg | Sun kWh/m²/day | Water, unheated | Water, covered | Heat pump $ | Gas $ |
|---|---|---|---|---|---|---|---|
| Jan | 55° | 44° | 2.3 | 43° | 49° | – | – |
| Feb | 58° | 46° | 3.3 | 45° | 51° | – | – |
| Mar | 62° | 49° | 4.6 | 49° | 55° | – | – |
| Apr | 66° | 53° | 6.1 | 54° | 60° | – | – |
| May | 73° | 59° | 7.3 | 60° | 66° | $286 | $355 |
| Jun | 83° | 67° | 8.1 | 68° | 74° | $106 | $148 |
| Jul | 91° | 74° | 8.0 | 76° | 82° | – | – |
| Aug | 91° | 72° | 7.1 | 77° | 83° | – | – |
| Sep | 85° | 68° | 5.8 | 73° | 79° | $18 | $26 |
| Oct | 75° | 59° | 4.2 | 65° | 71° | $188 | $235 |
| Nov | 63° | 50° | 2.8 | 54° | 60° | – | – |
| Dec | 55° | 44° | 2.0 | 46° | 52° | – | – |
Heating costs most in May (about $286 with a heat pump, $355 with gas). Sunshine peaks in Jun at 8.1 kWh/m²/day (NASA satellite data, 52.4 km grid cell). Highlighted months are swimmable with no heater.
How Clearlake compares with nearby cities
Clearlake ranks 209 of 376 California cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Healdsburg, CA | 26 mi | 0 | 7 | $652 |
| Windsor, CA | 30 mi | 0 | 6 | $657 |
| Ukiah, CA | 33 mi | 0 | 6 | $467 |
| Santa Rosa, CA | 36 mi | 0 | 7 | $934 |
| Rohnert Park, CA | 42 mi | 0 | 7 | $934 |
| Sonoma, CA | 47 mi | 0 | 6 | $496 |